Advances in multi-slice Computed Tomography (CT) technology have enabled the increased utilization of Dynamic Contrast Enhanced (DCE) CT in a clinical setting. By cine scanning (i.e., obtaining time series images) at relatively short time intervals, tissue and vascular enhancement can be measured and tracked over time to give uptake curves from which the distribution of contrast agent in tissue can be modeled. Different parameter models for contrast material exchange have been developed, for example to quantify tissue perfusion, vascular permeability, and blood volume and plasma mean transit time15, 22-28. The term ‘perfusion’ may be used to refer to blood flow only, however ‘perfusion CT’ (pCT) may also be used to refer to the derivation of other functional parameters (e.g., as listed above) from conventional DCE-CT measurements. In the present disclosure, perfusion CT is used to refer to the use of CT for deriving flow parameters not limited to blood flow.
Perfusion CT may be used in various levels of cancer treatment, including, for example, from the staging & detection of disease3-5, assessment of tumor micro-vascularity1, 2, improved target definition, predict radiation-induced normal tissue damage after radiotherapy6-10 and response to treatment46. An imaging method for perfusion studies has historically been MRI, which may provide a relatively large field-of-view (FOV). CT scanners have been developed allowing for wide-volumetric scans (e.g., as much as 16 cm in 350 msec). These 4D scanners may be useful over 2D dynamic scanners, for example where breathing induced anatomical motion can limit scan frequency and accuracy. This may offer the potential for relatively robust perfusion imaging which can tolerate a relative degree of motion. Furthermore, the potentially complex relationship between MRI signal and contrast kinetics and long acquisition times may be circumvented with CT, which may provide more simplicity in quantification through the relative linearity of CT enhancement to contrast concentration. X-ray therapy and diagnosis are used in management of cancer patients receiving radiation therapy (RT), where the risk associated with the additional radiation exposure from DCE-CT imaging may be factored differently. Additionally, the ability to add DCE-CT to conventional anatomical CT examinations, which may be commonly available and relatively low cost, may make DCE-CT useful for cancer therapy.